$columns: 12;

.row {
    display: flex;
    flex-wrap: wrap;
    margin: 0px;
    padding: 0px;
}

@for $i from 1 through $columns {
    .col-#{$i} {
        flex: 0 0 percentage($i / $columns);
        max-width: percentage($i / $columns);
    }
}